Zoledronate Attenuates Accumulation of DNA Damage in Mesenchymal Stem Cells and Protects Their Function

Running on empty: Exploring stem cell exhaustion in geriatric musculoskeletal disease

Ageing populations globally are associated with increased musculoskeletal disease, including osteoporosis and sarcopenia. These conditions place a significant burden of disease on the individual, society and the economy. To address this, we need to understand the underpinning biological changes, including stem cell exhaustion, which plays a key role in the ageing of the musculoskeletal system. This review of the recent evidence provides an overview of the associated biological processes. The review utilised the PubMed/Medline, Science Direct, and Google Scholar databases. Mechanisms of ageing identified involve a reaction to the chronic inflammation and oxidative stress associated with ageing, resulting in progenitor cell senescence and adipogenic differentiation, leading to decreased mass and quality of both bone and muscle tissue. Although the mechanisms underpinning stem cell exhaustion are unclear, it remains a promising avenue through which to identify new strategies for prevention, detection and management.

A Pragmatic Approach to Introducing Translational Geroscience Into the Clinic: A Paradigm Based on the Incremental Progression of Aging-Related Clinical Research

Geroscience posits that molecular drivers underlie the aging process. Gerotherapeutics entail strategies to counter molecular drivers of aging to reduce the chronic diseases and geriatric syndromes they trigger. Although the concept of gerotherapeutics for prevention has generated much excitement, the implications of prescribing potentially harmful medications to older adults who are "healthy" have been associated with many delays. Concerns regarding safety and valid endpoints have contributed to holdups. In contrast, it has been relatively easier to implement trials of medications with gerotherapeutic properties as novel approaches to remedy disease. In these applications, the risks of the medications are easier to justify when therapeutic benefits are perceived as outweighing the harms of the disease. Likewise, metrics of effective disease treatments are often seen as more reliable and quantifiable than metrics of health prolongation. Overall, clarifying geroscience mechanisms in disease therapeutic applications provides key opportunities to advance translational geroscience, especially as preventive geroscience trials are often encumbered. In this review, gerotherapeutic benefits of canakinumab, cholchicine, and zoledronic acid as parts of disease management are considered. Longevity Clinics and other opportunities to advance translational geroscience as parts of contemporary care are also discussed.

Effect of bisphosphonates and statins on the in vitro radiosensitivity of breast cancer cell lines

BACKGROUND

Early-stage breast cancer is usually treated with breast-conserving surgery followed by adjuvant radiation therapy. Acute skin toxicity is a common radiation-induced side effect experienced by many patients. Recently, a combination of bisphosphonates (zoledronic acid) and statins (pravastatin), or ZOPRA, was shown to radio-protect normal tissues by enhancing DNA double-strand breaks (DSB) repair mechanism. However, there are no studies assessing the effect of ZOPRA on cancerous cells. The purpose of this study is to characterize the in vitro effect of the zoledronic acid (ZO), pravastatin (PRA), and ZOPRA treatment on the molecular and cellular radiosensitivity of breast cancer cell lines.

MATERIALS

Two breast cancer cell lines, MDA MB 231 and MCF-7, were tested. Cells were treated with different concentrations of pravastatin (PRA), zoledronate (ZO), as well as their ZOPRA combination, before irradiation. Anti-γH2AX and anti-pATM immunofluorescence were performed to study DNA DSB repair kinetics. MTT assay was performed to assess cell proliferation and viability, and flow cytometry was performed to analyze the effect of the drugs on the cell cycle distribution. The clonogenic assay was used to assess cell survival.

RESULTS

ZO, PRA, and ZOPRA treatments were shown to increase the residual number of γH2AX foci for both cell lines. ZOPRA treatment was also shown to reduce the activity of the ATM kinase in MCF-7. ZOPRA induced a significant decrease in cell survival for both cell lines.

CONCLUSIONS

Our findings show that pretreatment with ZOPRA can decrease the radioresistance of breast cancer cells at the molecular and cellular levels. The fact that ZOPRA was previously shown to radioprotect normal tissues, makes it a good candidate to become a therapeutic window-widening drug.

Anti-osteoporosis drugs reduce mortality in cancer patients: A national cohort study of elderly with vertebral fractures

Introduction

The most prevalent type of fragility fractures is osteoporotic vertebral fractures (OVFs). However, only a few studies have examined the relationship between anti-osteoporosis treatments and malignancy-related mortality following an OVF. The goal of this study is to determine the effect of anti-osteoporosis therapy on mortality in OVF patients with and without cancer.

Method

Data from older people over the age of 65 who were hospitalised for OVFs between 1 January 2003 and 31 December 2018 were analysed retrospectively. A total of 6139 persons getting osteoporosis treatment and 28,950 who did not receive treatment were analysed, together with 2 sets of patients, comprising cancer patients (794) and cancer-free patients (5342), using anti-osteoporosis medication or not, in 1:1 propensity score-matched analyses. The hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated.

Results

In all, 35,089 patients with OVFs were included in the population; 29,931 people (85.3%) were women, and the mean (standard deviation) age was 78.13 (9.27) years. Overall survival was considerably higher in those undergoing osteoporosis therapy. This was true both for those without cancer (adjusted HR 0.55; 95% CI 0.51-0.59; P<.0001) as well as those with cancer (adjusted HR 0.72; 95% CI 0.62-0.84; P<.0001). Even among cancer patients, those who received anti-osteoporotic drugs had a lower mortality rate than those who did not.

Conclusion

Our findings suggest that anti-osteoporosis therapy should be initiated regardless of the presence of cancer in the elderly, as it increases survival following OVFs.

GDF15 Modulates the Zoledronic-Acid-Induced Hyperinflammatory Mechanoresponse of Periodontal Ligament Fibroblasts

Orthodontic tooth movement (OTM) is thought to be impeded by bisphosphonate (BP) therapy, mainly due to increased osteoclast apoptosis and changes in the periodontal ligament (PdL), a connecting tissue between the alveolar bone and teeth. PdL cells, mainly fibroblasts (PdLFs), are crucial regulators in OTM by modulating force-induced local inflammatory processes. Recently, we identified the TGF-β/BMP superfamily member GDF15 as an important modulator in OTM, promoting the pro-inflammatory mechanoresponses of PdLFs. The precise impact of the highly potent BP zoledronate (ZOL) on the mechanofunctionality of PdLFs is still under-investigated. Therefore, the aim of this study was to further characterize the ZOL-induced changes in the initial inflammatory mechanoresponse of human PdLFs (hPdLFs) and to further clarify a potential interrelationship with GDF15 signaling. Thus, two-day in vitro treatment with 0.5 µM, 5 µM and 50 µM of ZOL altered the cellular properties of hPdLFs partially in a concentration-dependent manner. In particular, exposure to ZOL decreased their metabolic activity, the proliferation rate, detected using Ki-67 immunofluorescent staining, and survival, analyzed using trypan blue. An increasing occurrence of DNA strand breaks was observed using TUNEL and an activated DNA damage response was demonstrated using H2A.X (phosphoS139) staining. While the osteogenic differentiation of hPdLFs was unaffected by ZOL, increased cellular senescence was observed using enhanced p21Waf1/Cip1/Sdi1 and β-galactosidase staining. In addition, cytokine-encoding genes such as IL6, IL8, COX2 and GDF15, which are associated with a senescence-associated secretory phenotype, were up-regulated by ZOL. Subsequently, this change in the hPdLF phenotype promoted a hyperinflammatory response to applied compressive forces with an increased expression of the pro-inflammatory markers IL1β, IL6 and GDF15, as well as the activation of monocytic THP1 cells. GDF15 appeared to be particularly relevant to these changes, as siRNA-mediated down-regulation balanced these hyperinflammatory responses by reducing IL-1β and IL-6 expression (IL1B p-value < 0.0001; IL6 p-value < 0.001) and secretion (IL-1β p-value < 0.05; IL-6 p-value < 0.001), as well as immune cell activation (p-value < 0.0001). In addition, ZOL-related reduced RANKL/OPG values and inhibited osteoclast activation were enhanced in GDF15-deficient hPdLFs (both p-values < 0.0001; all statistical tests: one-way ANOVA, Tukey's post hoc test). Thus, GDF15 may become a promising new target in the personalized orthodontic treatment of bisphosphonatepatients.

Bisphosphonates as Radiopharmaceuticals: Spotlight on the Development and Clinical Use of DOTAZOL in Diagnostics and Palliative Radionuclide Therapy

Bisphosphonates are therapeutic agents that have been used for almost five decades in the treatment of various bone diseases, such as osteoporosis, Paget disease and prevention of osseous complications in cancer patients. In nuclear medicine, simple bisphosphonates such as 99mTc-radiolabelled oxidronate and medronate remain first-line bone scintigraphic imaging agents for both oncology and non-oncology indications. In line with the growing interest in theranostic molecules, bifunctional bisphosphonates bearing a chelating moiety capable of complexing a variety of radiometals were designed. Among them, DOTA-conjugated zoledronate (DOTAZOL) emerged as an ideal derivative for both PET imaging (when radiolabeled with 68Ga) and management of bone metastases from various types of cancer (when radiolabeled with 177Lu). In this context, this report provides an overview of the main medicinal chemistry aspects concerning bisphosphonates, discussing their roles in molecular oncology imaging and targeted radionuclide therapy with a particular focus on bifunctional bisphosphonates. Particular attention is also paid to the development of DOTAZOL, with emphasis on the radiochemistry and quality control aspects of its preparation, before outlining the preclinical and clinical data obtained so far with this radiopharmaceutical candidate.

Challenges in developing Geroscience trials

Geroscience is becoming a major hope for preventing age-related diseases and loss of function by targeting biological mechanisms of aging. This unprecedented paradigm shift requires optimizing the design of future clinical studies related to aging in humans. Researchers will face a number of challenges, including ideal populations to study, which lifestyle and Gerotherapeutic interventions to test initially, selecting key primary and secondary outcomes of such clinical trials, and which age-related biomarkers are most valuable for both selecting interventions and predicting or monitoring clinical responses ("Gerodiagnostics"). This article reports the main results of a Task Force of experts in Geroscience.

In vitro and in vivo effects of zoledronic acid on senescence and senescence-associated secretory phenotype markers

In addition to reducing fracture risk, zoledronic acid has been found in some studies to decrease mortality in humans and extend lifespan and healthspan in animals. Because senescent cells accumulate with aging and contribute to multiple co-morbidities, the non-skeletal actions of zoledronic acid could be due to senolytic (killing of senescent cells) or senomorphic (inhibition of the secretion of the senescence-associated secretory phenotype [SASP]) actions. To test this, we first performed in vitro senescence assays using human lung fibroblasts and DNA repair-deficient mouse embryonic fibroblasts, which demonstrated that zoledronic acid killed senescent cells with minimal effects on non-senescent cells. Next, in aged mice treated with zoledronic acid or vehicle for 8 weeks, zoledronic acid significantly reduced circulating SASP factors, including CCL7, IL-1β, TNFRSF1A, and TGFβ1 and improved grip strength. Analysis of publicly available RNAseq data from CD115+ (CSF1R/c-fms+) pre-osteoclastic cells isolated from mice treated with zoledronic acid demonstrated a significant downregulation of senescence/SASP genes (SenMayo). To establish that these cells are potential senolytic/senomorphic targets of zoledronic acid, we used single cell proteomic analysis (cytometry by time of flight [CyTOF]) and demonstrated that zoledronic acid significantly reduced the number of pre-osteoclastic (CD115+/CD3e-/Ly6G-/CD45R-) cells and decreased protein levels of p16, p21, and SASP markers in these cells without affecting other immune cell populations. Collectively, our findings demonstrate that zoledronic acid has senolytic effects in vitro and modulates senescence/SASP biomarkers in vivo. These data point to the need for additional studies testing zoledronic acid and/or other bisphosphonate derivatives for senotherapeutic efficacy.

Refracture risk and all-cause mortality after vertebral fragility fractures: Anti-osteoporotic medications matter

BACKGROUND

Osteoporotic vertebral fractures may predict the future occurrence of fractures and increase mortality. Treating underlying osteoporosis may prevent second fractures. However, whether anti-osteoporotic treatment can reduce the mortality rate is not clear. The aim of this population study was to identify the degree of decreased mortality following the use of anti-osteoporotic medication after vertebral fractures.

METHODS

We identified patients who had newly diagnosed osteoporosis and vertebral fractures from 2009 to 2019 using the Taiwan National Health Insurance Research Database (NHIRD). We used national death registration data to determine the overall mortality rate.

RESULTS

There were 59,926 patients with osteoporotic vertebral fractures included in this study. After excluding patients with short-term mortality, patients who had previously received anti-osteoporotic medications had a lower refracture rate as well as a lower mortality risk (hazard ratio (HR): 0.84, 95% confidence interval (CI): 0.81-0.88). Patients receiving treatment for more than 3 years had a much lower mortality risk (HR: 0.53, 95% CI: 0.50-0.57). Patients who used oral bisphosphonates (alendronate and risedronate, HR: 0.95, 95% CI: 0.90-1.00), intravenous zoledronic acid (HR: 0.83, 95% CI: 0.74-0.93), and subcutaneous denosumab injections (HR: 0.71, 95% CI: 0.65-0.77) had lower mortality rates than patients without further treatment after vertebral fractures.

CONCLUSION

In addition to fracture prevention, anti-osteoporotic treatments for patients with vertebral fractures were associated with a reduction in mortality. A longer duration of treatment and the use of long-acting drugs was also associated with lower mortality.

Rejuvenation of Mesenchymal Stem Cells to Ameliorate Skeletal Aging

Advanced age is a shared risk factor for many chronic and debilitating skeletal diseases including osteoporosis and periodontitis. Mesenchymal stem cells develop various aging phenotypes including the onset of senescence, intrinsic loss of regenerative potential and exacerbation of inflammatory microenvironment via secretory factors. This review elaborates on the emerging concepts on the molecular and epigenetic mechanisms of MSC senescence, such as the accumulation of oxidative stress, DNA damage and mitochondrial dysfunction. Senescent MSCs aggravate local inflammation, disrupt bone remodeling and bone-fat balance, thereby contributing to the progression of age-related bone diseases. Various rejuvenation strategies to target senescent MSCs could present a promising paradigm to restore skeletal aging.

In vitro and in vivo effects of zoledronate on senescence and senescence-associated secretory phenotype markers

In addition to reducing fracture risk, zoledronate has been found in some studies to decrease mortality in humans and extend lifespan and healthspan in animals. Because senescent cells accumulate with aging and contribute to multiple co-morbidities, the non-skeletal actions of zoledronate could be due to senolytic (killing of senescent cells) or senomorphic (inhibition of the secretion of the senescence-associated secretory phenotype [SASP]) actions. To test this, we first performed in vitro senescence assays using human lung fibroblasts and DNA repair-deficient mouse embryonic fibroblasts, which demonstrated that zoledronate killed senescent cells with minimal effects on non-senescent cells. Next, in aged mice treated with zoledronate or vehicle for 8 weeks, zoledronate significantly reduced circulating SASP factors, including CCL7, IL-1β, TNFRSF1A, and TGFβ1 and improved grip strength. Analysis of publicly available RNAseq data from CD115+ (CSF1R/c-fms+) pre-osteoclastic cells isolated from mice treated with zoledronate demonstrated a significant downregulation of senescence/SASP genes (SenMayo). To establish that these cells are potential senolytic/senomorphic targets of zoledronate, we used single cell proteomic analysis (cytometry by time of flight [CyTOF]) and demonstrated that zoledronate significantly reduced the number of pre-osteoclastic (CD115+/CD3e-/Ly6G-/CD45R-) cells and decreased protein levels of p16, p21, and SASP markers in these cells without affecting other immune cell populations. Collectively, our findings demonstrate that zoledronate has senolytic effects in vitro and modulates senescence/SASP biomarkers in vivo . These data point to the need for additional studies testing zoledronate and/or other bisphosphonate derivatives for senotherapeutic efficacy.

Aging and Bone Metabolism

Changes in bone architecture and metabolism with aging increase the likelihood of osteoporosis and fracture. Age-onset osteoporosis is multifactorial, with contributory extrinsic and intrinsic factors including certain medical problems, specific prescription drugs, estrogen loss, secondary hyperparathyroidism, microenvironmental and cellular alterations in bone tissue, and mechanical unloading or immobilization. At the histological level, there are changes in trabecular and cortical bone as well as marrow cellularity, lineage switching of mesenchymal stem cells to an adipogenic fate, inadequate transduction of signals during skeletal loading, and predisposition toward senescent cell accumulation with production of a senescence-associated secretory phenotype. Cumulatively, these changes result in bone remodeling abnormalities that over time cause net bone loss typically seen in older adults. Age-related osteoporosis is a geriatric syndrome due to the multiple etiologies that converge upon the skeleton to produce the ultimate phenotypic changes that manifest as bone fragility. Bone tissue is dynamic but with tendencies toward poor osteoblastic bone formation and relative osteoclastic bone resorption with aging. Interactions with other aging physiologic systems, such as muscle, may also confer detrimental effects on the aging skeleton. Conversely, individuals who maintain their BMD experience a lower risk of fractures, disability, and mortality, suggesting that this phenotype may be a marker of successful aging. © 2023 American Physiological Society. Compr Physiol 13:4355-4386, 2023.

Aging of mesenchymal stem cell: machinery, markers, and strategies of fighting

Human mesenchymal stem cells (MSCs) are primary multipotent cells capable of differentiating into osteocytes, chondrocytes, and adipocytes when stimulated under appropriate conditions. The role of MSCs in tissue homeostasis, aging-related diseases, and cellular therapy is clinically suggested. As aging is a universal problem that has large socioeconomic effects, an improved understanding of the concepts of aging can direct public policies that reduce its adverse impacts on the healthcare system and humanity. Several studies of aging have been carried out over several years to understand the phenomenon and different factors affecting human aging. A reduced ability of adult stem cell populations to reproduce and regenerate is one of the main  contributors to the human aging process. In this context, MSCs senescence is a major challenge in front of cellular therapy advancement. Many factors, ranging from genetic and metabolic pathways to extrinsic factors through various cellular signaling pathways, are involved in regulating the mechanism of MSC senescence. To better understand and reverse cellular senescence, this review highlights the underlying mechanisms and signs of MSC cellular senescence, and discusses the strategies to combat aging and cellular senescence.

Bibliometric and visual analysis of mesenchymal stem cells in the treatment of osteoporosis based on CiteSpace software

BACKGROUND

The focus of research in the treatment of osteoporosis (OP) has evolved from promoting bone formation and inhibiting bone resorption to current stem cell therapy. Due to their multipotent differentiation properties, mesenchymal stem cells (MSCs) can repair degenerated bones through transplantation, and have become a new method for the treatment of OP.

METHODS

Relevant literatures included in the Web of Science database core collection database from 2012 to 2021 were retrieved. CiteSpace software was used to analyze the cooperative relationship among authors, journals, institutions, and countries, and to analyze the co-citation situation of the literature. And performed co-occurrence analysis, cluster analysis and burst analysis of keywords, draw visual maps and analyzed the results.

RESULTS

A total of 2100 papers were included, and the number of papers published from 2012 to 2021 was on the rise. A total of 484 authors were included, and 176 authors published more than 3 papers. The high-yield authors were mainly represented by YAN JIN and BO GAO. A total of 99 journals were included, and the journal with the most publications was J BONE MINER RES. A total of 787 institutions were included, and the institution with the largest number of publications was Shanghai Jiao Tong University. A total of 65 countries were included. The country with the largest number of publications was China, and the United States had the highest centrality. The co-citation analysis of the literature found 2 articles with high citation frequency and high centrality. The main research direction was the mechanism of MSCs in the treatment of osteoporosis. A total of 133 keywords were included, and the hot keywords were osteogenic differentiation, expression, proliferation, bone marrow, etc.

CONCLUSIONS

The research hotspots in this field mainly focused on the mechanism of bone regeneration, proliferation and osteogenic differentiation of bone marrow MSCs, and the expression of osteogenic-related genes. The future research trends in this field are predicted to be the mechanism of action of microRNA and long non-coding RNA on MSCs and their relationship with OP, the mechanism of MSCs adipogenic and osteogenic differentiation, and tissue engineering scaffolds applications.

Zoledronate Extends Health Span and Survival via the Mevalonate Pathway in a FOXO-dependent Manner

Over recent decades, increased longevity has not been paralleled by extended health span, resulting in more years spent with multiple diseases in older age. As such, interventions to improve health span are urgently required. Zoledronate (Zol) is a nitrogen-containing bisphosphonate, which inhibits the farnesyl pyrophosphate synthase enzyme, central to the mevalonate pathway. It is already used clinically to prevent fractures in osteoporotic patients, who have been reported to derive unexpected and unexplained survival benefits. Using Drosophila as a model we determined the effects of Zol on life span, parameters of health span (climbing ability and intestinal dysplasia), and the ability to confer resistance to oxidative stress using a combination of genetically manipulated Drosophila strains and Western blotting. Our study shows that Zol extended life span, improved climbing activity, and reduced intestinal epithelial dysplasia and permeability with age. Mechanistic studies showed that Zol conferred resistance to oxidative stress and reduced accumulation of X-ray-induced DNA damage via inhibition of farnesyl pyrophosphate synthase. Moreover, Zol was associated with inhibition of phosphorylated AKT in the mammalian traget of rapamycin pathway downstream of the mevalonate pathway and required dFOXO for its action, both molecules associated with increased longevity. Taken together, our work indicates that Zol, a drug already widely used to prevent osteoporosis and dosed only once a year, modulates important mechanisms of aging. Its repurposing holds great promise as a treatment to improve health span.

The Impact of Various Anti-Osteoporosis Drugs on All-Cause Mortality After Hip Fractures: A Nationwide Population Study

Anti-osteoporosis treatment following hip fractures may reduce the overall mortality rate. However, the effects of different drugs on mortality is still unclear. This population-based cohort study aimed to identify the degree of reduced mortality after various anti-osteoporosis regimens following hip fracture surgery. We conducted this cohort study to identify patients with newly diagnosed osteoporosis and hip fractures from 2009 to 2017 using the Taiwan National Health Insurance Research Database (NHIRD). The subsequent use of anti-osteoporosis medication following hip fracture surgery was collected and analyzed. National death registration records were retrieved to determine mortality. A total of 45,226 new cases of osteoporotic hip fracture were identified. Compared with patients who did not receive further treatment, patients who had ever used oral bisphosphonates (alendronate and risedronate, hazard ratio [HR] 0.81; 95% confidence interval [CI], 0.78-0.84), ibandronate (HR 0.76; 95% CI, 0.67-0.86), zoledronic acid (HR 0.70; 95% CI, 0.64-0.76), and denosumab (HR 0.64; 95% CI, 0.60-0.68) showed lower all-cause mortality rates. Patients treated with bisphosphonates had a lower mortality risk than those treated with selective estrogen receptor modulators (HR 0.81; 95% CI, 0.75-0.87). Patients treated with zoledronic acid showed a lower mortality risk than those treated with oral bisphosphonates (HR 0.89; 95% CI, 0.82-0.97). However, patients receiving denosumab and zoledronic acid did not show a significant difference in mortality (HR 0.94; 95% CI, 0.85-1.03). Different anti-osteoporosis treatments for postsurgical patients were associated with different levels of decline in mortality. Generally, longer durations of drug use were associated with lower mortality. © 2022 American Society for Bone and Mineral Research (ASBMR).

Reduced All-Cause Mortality with Bisphosphonates Among Post-Fracture Osteoporosis Patients: A Nationwide Study and Systematic Review

We assessed the survival outcomes associated with real-world bisphosphonate use, stratified by fracture site, type, administration, and duration of treatment, among patients with osteoporosis. A systematic review that incorporates our findings was conducted to provide up-to-date evidence on survival outcomes with bisphosphonate treatment in real-world settings. Patients diagnosed with osteoporosis who had been hospitalized for major fractures were identified from Taiwan's National Health Insurance Research Database 2008-2017 and followed until 2018. There were 24,390 new bisphosphonate users who were classified and compared with 76,725 nonusers of anti-osteoporosis medications in terms of survival outcomes using Cox model analysis. An inverse probability of treatment weighted Cox model and landmark analyses for minimizing immortal time bias were also performed. Bisphosphonate users vs. nonusers had a significantly lower mortality risk, regardless of fracture site (hazard ratios (95% confidence intervals) for patients with any major fracture, hip fracture, and vertebral fracture: 0.90 (0.88, 0.93), 0.83 (0.80, 0.86), and 0.86 (0.82, 0.89), respectively). Compared with nonuse, zoledronic acid (0.77 (0.73, 0.82)) was associated with the lowest mortality, followed by ibandronate (0.85 (0.78, 0.93)) and alendronate/risedronate (0.93 (0.91, 0.96)). Using bisphosphonates for ≥ 3 years had lower mortality (0.60 (0.53, 0.67)) than using bisphosphonates for < 3 years (0.98 (0.95, 1.01)). Intravenous bisphosphonates had a lower mortality than that of oral bisphosphonates. Our results are consistent with the systematic review findings among real-world populations. In conclusion, bisphosphonate use, especially persistence to intravenous bisphosphonates (e.g., zoledronic acid), may reduce post-fracture mortality among patients with osteoporosis, particularly those with hip/vertebral fractures. This supports the rational use of bisphosphonates in post-fracture care.

Crosstalk Between Senescent Bone Cells and the Bone Tissue Microenvironment Influences Bone Fragility During Chronological Age and in Diabetes

Bone is a complex organ serving roles in skeletal support and movement, and is a source of blood cells including adaptive and innate immune cells. Structural and functional integrity is maintained through a balance between bone synthesis and bone degradation, dependent in part on mechanical loading but also on signaling and influences of the tissue microenvironment. Bone structure and the extracellular bone milieu change with age, predisposing to osteoporosis and increased fracture risk, and this is exacerbated in patients with diabetes. Such changes can include loss of bone mineral density, deterioration in micro-architecture, as well as decreased bone flexibility, through alteration of proteinaceous bone support structures, and accumulation of senescent cells. Senescence is a state of proliferation arrest accompanied by marked morphological and metabolic changes. It is driven by cellular stress and serves an important acute tumor suppressive mechanism when followed by immune-mediated senescent cell clearance. However, aging and pathological conditions including diabetes are associated with accumulation of senescent cells that generate a pro-inflammatory and tissue-destructive secretome (the SASP). The SASP impinges on the tissue microenvironment with detrimental local and systemic consequences; senescent cells are thought to contribute to the multimorbidity associated with advanced chronological age. Here, we assess factors that promote bone fragility, in the context both of chronological aging and accelerated aging in progeroid syndromes and in diabetes, including senescence-dependent alterations in the bone tissue microenvironment, and glycation changes to the tissue microenvironment that stimulate RAGE signaling, a process that is accelerated in diabetic patients. Finally, we discuss therapeutic interventions targeting RAGE signaling and cell senescence that show promise in improving bone health in older people and those living with diabetes.

Bisphosphonates: The role of chemistry in understanding their biological actions and structure-activity relationships, and new directions for their therapeutic use

The bisphosphonates ((HO)2P(O)CR1R2P(O)(OH)2, BPs) were first shown to inhibit bone resorption in the 1960s, but it was not until 30 years later that a detailed molecular understanding of the relationship between their varied chemical structures and biological activity was elucidated. In the 1990s and 2000s, several potent bisphosphonates containing nitrogen in their R2 side chains (N-BPs) were approved for clinical use including alendronate, risedronate, ibandronate, and zoledronate. These are now mostly generic drugs and remain the leading therapies for several major bone-related diseases, including osteoporosis and skeletal-related events associated with bone metastases. The early development of chemistry in this area was largely empirical and only a few common structural features related to strong binding to calcium phosphate were clear. Attempts to further develop structure-activity relationships to explain more dramatic pharmacological differences in vivo at first appeared inconclusive, and evidence for mechanisms underlying cellular effects on osteoclasts and macrophages only emerged after many years of research. The breakthrough came when the intracellular actions on the osteoclast were first shown for the simpler bisphosphonates, via the in vivo formation of P-C-P derivatives of ATP. The synthesis and biological evaluation of a large number of nitrogen-containing bisphosphonates in the 1980s and 1990s led to the key discovery that the antiresorptive effects of these more complex analogs on osteoclasts result mostly from their potency as inhibitors of the enzyme farnesyl diphosphate synthase (FDPS/FPPS). This key branch-point enzyme in the mevalonate pathway of cholesterol biosynthesis is important for the generation of isoprenoid lipids that are utilized for the post-translational modification of small GTP-binding proteins essential for osteoclast function. Since then, it has become even more clear that the overall pharmacological effects of individual bisphosphonates on bone depend upon two key properties: the affinity for bone mineral and inhibitory effects on biochemical targets within bone cells, in particular FDPS. Detailed enzyme-ligand crystal structure analysis began in the early 2000s and advances in our understanding of the structure-activity relationships, based on interactions with this target within the mevalonate pathway and related enzymes in osteoclasts and other cells have continued to be the focus of research efforts to this day. In addition, while many members of the bisphosphonate drug class share common properties, now it is more clear that chemical modifications to create variations in these properties may allow customization of BPs for different uses. Thus, as the appreciation for new potential opportunities with this drug class grows, new chemistry to allow ready access to an ever-widening variety of bisphosphonates continues to be developed. Potential new uses of the calcium phosphate binding mechanism of bisphosphonates for the targeting of other drugs to the skeleton, and effects discovered on other cellular targets, even at non-skeletal sites, continue to intrigue scientists in this research field.

Treatment of osteoporosis after hip fracture is associated with lower all-cause mortality: A nationwide population study

PURPOSE

Mortality after osteoporotic hip fractures is high. Postoperative care is as important as surgery itself to prevent a second fracture and improve outcomes, and the effect of anti-osteoporosis treatment after hip fractures on overall mortality is controversial. This nationwide population study aimed to determine whether anti-osteoporosis treatment might reduce overall mortality after hip fracture surgery.

METHODS

We conducted this cohort study using the National Health Insurance Research Database (NHIRD) of Taiwan to identify patients admitted for surgery due to hip fractures from 2008 to 2018. The subsequent use and duration of anti-osteoporotic medication and other parameters were analyzed, and national death registration records were retrieved to investigate mortality.

RESULTS

A total of 59,943 patients admitted for hip fracture surgery were identified. The 22,494 patients (37.5%) who received anti-osteoporotic medication showed a lower all-cause mortality rate compared with the 37,449 patients (62.5%) who did not receive further treatment (hazard ratio (HR): 0.69, 95% confidence interval (CI): 0.67-0.70, p < 0.0001). Patients who received anti-osteoporotic medication for more than 1, 2, and 3 years exhibited propotional reductions in all-cause mortality (HR & 95%CI: 0.57 (0.54-0.60), 0.42 (0.38-0.46), and 0.29 (0.26-0.33) respectively).

CONCLUSION

Anti-osteoporosis treatment was associated with lower all-cause mortality after hip fracture surgery. A longer duration of treatment was also associated with lower mortality. Postoperative treatment for osteoporosis is crucial for patients with hip fracture.

Disruption of FDPS/Rac1 axis radiosensitizes pancreatic ductal adenocarcinoma by attenuating DNA damage response and immunosuppressive signalling

Background

Radiation therapy (RT) has a suboptimal effect in patients with pancreatic ductal adenocarcinoma (PDAC) due to intrinsic and acquired radioresistance (RR). Comprehensive bioinformatics and microarray analysis revealed that cholesterol biosynthesis (CBS) is involved in the RR of PDAC. We now tested the inhibition of the CBS pathway enzyme, farnesyl diphosphate synthase (FDPS), by zoledronic acid (Zol) to enhance radiation and activate immune cells.

Methods

We investigated the role of FDPS in PDAC RR using the following methods: in vitro cell-based assay, immunohistochemistry, immunofluorescence, immunoblot, cell-based cholesterol assay, RNA sequencing, tumouroids (KPC-murine and PDAC patient-derived), orthotopic models, and PDAC patient's clinical study.

Findings

FDPS overexpression in PDAC tissues and cells (P < 0.01 and P < 0.05) is associated with poor RT response and survival (P = 0.024). CRISPR/Cas9 and pharmacological inhibition (Zol) of FDPS in human and mouse syngeneic PDAC cells in conjunction with RT conferred higher PDAC radiosensitivity in vitro (P < 0.05, P < 0.01, and P < 0.001) and in vivo (P < 0.05). Interestingly, murine (P = 0.01) and human (P = 0.0159) tumouroids treated with Zol+RT showed a significant growth reduction. Mechanistically, RNA-Seq analysis of the PDAC xenografts and patients-PBMCs revealed that Zol exerts radiosensitization by affecting Rac1 and Rho prenylation, thereby modulating DNA damage and radiation response signalling along with improved systemic immune cells activation. An ongoing phase I/II trial (NCT03073785) showed improved failure-free survival (FFS), enhanced immune cell activation, and decreased microenvironment-related genes upon Zol+RT treatment.

Interpretation

Our findings suggest that FDPS is a novel radiosensitization target for PDAC therapy. This study also provides a rationale to utilize Zol as a potential radiosensitizer and as an immunomodulator in PDAC and other cancers.

Funding

National Institutes of Health (P50, P01, and R01).

Bone Aging, Cellular Senescence, and Osteoporosis

Changes in aging bone that lead to osteoporosis are mediated at multiple levels, including hormonal alterations, skeletal unloading, and accumulation of senescent cells. This pathological interplay is superimposed upon medical conditions, potentially bone-wasting medications, modifiable and unmodifiable personal risk factors, and genetic predisposition that accelerate bone loss with aging. In this study, the focus is on bone hemostasis and its dysregulation with aging. The major physiological changes with aging in bone and the role of cellular senescence in contributing to age-related osteoporosis are summarized. The aspects of bone aging are reviewed including remodeling deficits, uncoupling phenomena, inducers of cellular senescence related to bone aging, roles of the senescence-associated secretory phenotype, radiation-induced bone loss as a model for bone aging, and the accumulation of senescent cells in the bone microenvironment as a predominant mechanism for age-related osteoporosis. The study also addresses the rationale and potential for therapeutic interventions based on the clearance of senescent cells or suppression of the senescence-associated secretory phenotype. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Skeletal Aging and Osteoporosis: Mechanisms and Therapeutics

Bone is a dynamic organ maintained by tightly regulated mechanisms. With old age, bone homeostasis, which is maintained by an intricate balance between bone formation and bone resorption, undergoes deregulation. Oxidative stress-induced DNA damage, cellular apoptosis, and cellular senescence are all responsible for this tissue dysfunction and the imbalance in the bone homeostasis. These cellular mechanisms have become a target for therapeutics to treat age-related osteoporosis. Genetic mouse models have shown the importance of senescent cell clearance in alleviating age-related osteoporosis. Furthermore, we and others have shown that targeting cellular senescence pharmacologically was an effective tool to alleviate age- and radiation-induced osteoporosis. Senescent cells also have an altered secretome known as the senescence associated secretory phenotype (SASP), which may have autocrine, paracrine, or endocrine function. The current review discusses the current and potential pathways which lead to a senescence profile in an aged skeleton and how bone homeostasis is affected during age-related osteoporosis. The review has also discussed existing therapeutics for the treatment of osteoporosis and rationalizes for novel therapeutic options based on cellular senescence and the SASP as an underlying pathogenesis of an aging bone.

Culturing at Low Cell Density Delays Cellular Senescence of Human Bone Marrow-Derived Mesenchymal Stem Cells in Long-Term Cultures

Background and Objectives

Mesenchymal stem cells (MSCs) have immense therapeutic potential for treating intractable and immune diseases. They also have applications in regenerative medicine in which distinct treatments do not exist. Thus, MSCs are gaining attention as important raw materials in the field of cell therapy. Importantly, the number of MSCs in the bone marrow is limited and they are present only in small quantities. Therefore, mass production of MSCs through long-term culture is necessary to use them in cell therapy. However, MSCs undergo cellular senescence through repeated passages during mass production. In this study, we explored methods to prolong the limited lifetime of MSCs by culturing them with different seeding densities.

Methods and Results

We observed that in long-term cultures, low-density (LD, 50 cells/cm²) MSCs showed higher population doubling level, leading to greater fold increase, than high-density (HD, 4,000 cells/cm²) MSCs. LD-MSCs suppressed the expression of aging-related genes. We also showed that reactive oxygen species (ROS) were decreased in LD-MSCs compared to that in HD-MSCs. Further, proliferation potential increased when ROS were inhibited in HD-MSCs.

Conclusions

The results in this study suggest that MSC senescence can be delayed and that life span can be extended by controlling cell density in vitro. These results can be used as important data for the mass production of stem cell therapeutic products.

Bisphosphonates in veterinary medicine: The new horizon for use

Bisphosphonates (BPs) are characterized by their ability to bind strongly to bone mineral and inhibit bone resorption. However, BPs exert a wide range of pharmacological activities beyond the inhibition of bone resorption, including the inhibition of cancer cell metastases and angiogenesis and the inhibition of proliferation and apoptosis in vitro. Additionally, the inhibition of matrix metalloproteinase activity, altered cytokine and growth factor expression, as well as reductions in parameters of pain have also been reported. In humans, clinical BP use has transformed the treatment of post-menopausal osteoporosis, rare bone diseases such as osteogenesis imperfecta, as well as multiple myeloma and metastatic breast and prostate cancer, albeit not without infrequent but significant adverse events. Despite the well-characterized health benefits of BP use in humans, the evidence-base for the therapeutic efficacy of BPs in veterinary medicine is, by comparison, limited. Notwithstanding, BPs are used widely in small animal veterinary practice for the medical management of hyperparathyroidism, idiopathic hypercalcemia in cats, as well as for the palliative care of bone tumors which are common in dogs, and in particular, primary bone tumors such as osteosarcoma. Palliative BP treatment has also recently increased in veterinary oncology to alleviate tumor-associated bone pain. In equine veterinary practice, non-nitrogen-containing BPs are FDA-approved to control clinical signs associated with navicular syndrome in adult horses. However, there are growing concerns regarding the off-label use of BPs in juvenile horses. Here we discuss the current understanding of the strengths, weaknesses and current controversies surrounding BP use in veterinary medicine to highlight the future utility of these potentially beneficial drugs.

Pleiotropic effects of statins: A focus on cancer

The statin drugs ('statins') potently inhibit hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase by competitively blocking the active site of the enzyme. Statins decrease de novo cholesterol biosynthesis and thereby reduce plasma cholesterol levels. Statins exhibit "pleiotropic" properties that are independent of their lipid-lowering effects. For example, preclinical evidence suggests that statins inhibit tumor growth and induce apoptosis in specific cancer cell types. Furthermore, statins show chemo-sensitizing effects by impairing Ras family GTPase signaling. However, whether statins have clinically meaningful anti-cancer effects remains an area of active investigation. Both preclinical and clinical studies on the potential mechanisms of action of statins in several cancers have been reviewed in the literature. Considering the contradictory data on their efficacy, we present an up-to-date summary of the pleiotropic effects of statins in cancer therapy and review their impact on different malignancies. We also discuss the synergistic anti-cancer effects of statins when combined with other more conventional anti-cancer drugs to highlight areas of potential therapeutic development.

Benefits of Bisphosphonate Therapy: Beyond the Skeleton

PURPOSE OF REVIEW

Recent evidence from clinical trials and observational studies raises the possibility that bisphosphonate use might confer a lower risk of cardiovascular disease and cancer, resulting in a mortality benefit. This review summarizes clinical and preclinical studies examining the non-skeletal effects of bisphosphonates.

RECENT FINDINGS

Data from clinical trials are conflicting regarding whether or not bisphosphonates have beneficial effects on mortality, cardiovascular events, or cancer incidence. No clinical trials have assessed these outcomes as primary endpoints, and most trials were shorter than 4 years. Observational data suggest that bisphosphonate users may have lower mortality, delayed progression of vascular calcification and atherosclerotic burden, and reduced incidence of breast and colorectal cancer compared to non-users. Preclinical studies confirm that bisphosphonates can be taken up by macrophages and monocytes, and nitrogen-containing bisphosphonates have the ability to disrupt the mevalonate pathway within these cells. In this manner, bisphosphonates exert anti-atherogenic and anti-cancer effects. Bisphosphonates also appear to exert protective effects on vascular smooth muscle cells and endothelial cells and may have direct cytotoxic effects on cancer cells. The balance of evidence does not support bisphosphonate treatment for the primary purpose of improving non-skeletal outcomes, although appropriately designed controlled trials that further explore this possibility are both justified and required. Patients with skeletal indications for bisphosphonate therapy can be reassured that these agents are not associated with increased mortality, cardiovascular disease, or cancer incidence.

Zoledronate

Zoledronate is the most potent and most long-acting bisphosphonate in clinical use, and is administered as an intravenous infusion. Its major uses are in osteoporosis, Paget's disease, and in myeloma and cancers to reduce adverse skeletal related events (SREs). In benign disease, it is a first- or second-line treatment for osteoporosis, achieving anti-fracture efficacy comparable to that of the RANKL blocker, denosumab, over 3 years, and it reduces fracture risk in osteopenic older women. It is the preferred treatment for Paget's disease, achieving higher rates of remissions which are much more prolonged than with any other agent. Some trials have suggested that it reduces mortality, cardiovascular disease and cancer, but these findings are not consistent across all studies. It is nephrotoxic, so should not be given to those with significant renal impairment, and, like other potent anti-resorptive agents, can cause hypocalcemia in patients with severe vitamin D deficiency, which should be corrected before administration. Its most common adverse effect is the acute phase response, seen in 30-40% of patients after their first dose, and much less commonly subsequently. Clinical trials in osteoporosis have not demonstrated increases in osteonecrosis of the jaw or in atypical femoral fractures. Observational databases are currently inadequate to determine whether these problems are increased in zoledronate users. Now available as a generic, zoledronate is a cost-effective agent for fracture prevention and for management of Paget's disease, but wider provision of infusion facilities is important to increase patient access. There is a need to further explore its potential for reducing cancer, cardiovascular disease and mortality, since these effects could be substantially more important than its skeletal actions.

Association Between Drug Treatments for Patients With Osteoporosis and Overall Mortality Rates: A Meta-analysis

IMPORTANCE

Previous studies have reported that drug treatments, particularly treatment with bisphosphonates, is associated with reduced overall mortality rates in addition to decreased fracture risk. If so, drug treatments should be recommended for this reason alone, regardless of a patient's risk of fracture.

OBJECTIVE

To assess whether randomized clinical trials demonstrate that treatment with bisphosphonates, particularly zoledronate, is associated with reduced mortality rates.

DATA SOURCES

Science Direct, MEDLINE, Embase, and the Cochrane Library were searched for randomized placebo-controlled clinical trials of drug treatments for osteoporosis published after 2009 and published or in press before April 19, 2019. Conference abstracts from annual osteoporosis society meetings were also included in the search.

STUDY SELECTION

Included studies were clinical trials that (1) were randomized and placebo-controlled; (2) studied drug treatments with proven antifracture efficacy; (3) used agents at the approved dose for treatment of osteoporosis; and (4) had a duration of 1 year or more. Abstracts from the literature searches were reviewed for inclusion and exclusion criteria, and mortality rate data were abstracted from the article by 1 researcher and validated by a second. A total of 2045 records were screened; 38 (1.8%) were included in the meta-analyses.

DATA EXTRACTION AND SYNTHESIS

The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) checklist was followed for abstracting data and assessing data quality and validity. Data were pooled using random-effects models, and between-study variability was assessed using the I2 index. The risk of bias for each study was assessed, and funnel plots and Egger and Begg statistics were used to evaluate publication bias.

MAIN OUTCOMES AND MEASURES

Associations of all drug treatments, particularly bisphosphonate and zoledronate treatments, with overall mortality.

RESULTS

Of 38 clinical trials that included 101 642 unique participants, 38 were included in the meta-analyses of all drug treatments (45 594 participants randomized to placebo; 56 048 to treatment); 21 clinical trials, of bisphosphonate treatments (20 244 participants randomized to placebo; 22 623 to treatment); and 6 clinical trials, of zoledronate treatments (6944 participants randomized to placebo; 6926 to treatment). No significant association was found between all drug treatments for osteoporosis and overall mortality rate (risk ratio [RR], 0.98; 95% CI, 0.91-1.05; I2 = 0%). Clinical trials of bisphosphonate treatment (RR, 0.95; 95% CI, 0.86-1.04) showed no significant association with overall mortality. Also, clinical trials of zoledronate treatment (RR, 0.88; 95% CI, 0.68-1.13) showed no association with overall mortality rate; however, evidence existed for heterogeneity of the results (I2 = 48.2%).

CONCLUSIONS AND RELEVANCE

Results of this meta-analysis suggest that bisphosphonate treatment may not be associated with reduced overall mortality rates in addition to decreased fracture risk and should only be recommended to reduce fracture risk. Additional trials are needed to clarify whether treatment with zoledronate reduces mortality rates.

Pharmacology of bisphosphonates

The biological effects of the bisphosphonates (BPs) as inhibitors of calcification and bone resorption were first described in the late 1960s. In the 50 years that have elapsed since then, the BPs have become the leading drugs for the treatment of skeletal disorders characterized by increased bone resorption, including Paget's disease of bone, bone metastases, multiple myeloma, osteoporosis and several childhood inherited disorders. The discovery and development of the BPs as a major class of drugs for the treatment of bone diseases is a paradigm for the successful journey from "bench to bedside and back again". Several of the leading BPs achieved "blockbuster" status as branded drugs. However, these BPs have now come to the end of their patent life, making them highly affordable. The opportunity for new clinical applications for BPs also exists in other areas of medicine such as ageing, cardiovascular disease and radiation protection. Their use as inexpensive generic medicines is therefore likely to continue for many years to come. Fifty years of research into the pharmacology of bisphosphonates have led to a fairly good understanding about how these drugs work and how they can be used safely in patients with metabolic bone diseases. However, while we seemingly know much about these drugs, a number of key aspects related to BP distribution and action remain incompletely understood. This review summarizes the existing knowledge of the (pre)clinical and translational pharmacology of BPs, and highlights areas in which understanding is lacking.

Farnesyltransferase inhibitor and rapamycin correct aberrant genome organisation and decrease DNA damage respectively, in Hutchinson-Gilford progeria syndrome fibroblasts

Hutchinson–Gilford progeria syndrome (HGPS) is a rare and fatal premature ageing disease in children. HGPS is one of several progeroid syndromes caused by mutations in the LMNA gene encoding the nuclear structural proteins lamins A and C. In classic HGPS the mutation G608G leads to the formation of a toxic lamin A protein called progerin. During post-translational processing progerin remains farnesylated owing to the mutation interfering with a step whereby the farnesyl moiety is removed by the enzyme ZMPSTE24. Permanent farnesylation of progerin is thought to be responsible for the proteins toxicity. Farnesyl is generated through the mevalonate pathway and three drugs that interfere with this pathway and hence the farnesylation of proteins have been administered to HGPS children in clinical trials. These are a farnesyltransferase inhibitor (FTI), statin and a bisphosphonate. Further experimental studies have revealed that other drugs such as N-acetyl cysteine, rapamycin and IGF-1 may be of use in treating HGPS through other pathways. We have shown previously that FTIs restore chromosome positioning in interphase HGPS nuclei. Mis-localisation of chromosomes could affect the cells ability to regulate proper genome function. Using nine different drug treatments representing drug regimes in the clinic we have shown that combinatorial treatments containing FTIs are most effective in restoring specific chromosome positioning towards the nuclear periphery and in tethering telomeres to the nucleoskeleton. On the other hand, rapamycin was found to be detrimental to telomere tethering, it was, nonetheless, the most effective at inducing DNA damage repair, as revealed by COMET analyses.

Isoprenoids and protein prenylation: implications in the pathogenesis and therapeutic intervention of Alzheimer's disease

The mevalonate-isoprenoid-cholesterol biosynthesis pathway plays a key role in human health and disease. The importance of this pathway is underscored by the discovery that two major isoprenoids, farnesyl and geranylgeranyl pyrophosphate, are required to modify an array of proteins through a process known as protein prenylation, catalyzed by prenyltransferases. The lipophilic prenyl group facilitates the anchoring of proteins in cell membranes, mediating protein-protein interactions and signal transduction. Numerous essential intracellular proteins undergo prenylation, including most members of the small GTPase superfamily as well as heterotrimeric G proteins and nuclear lamins, and are involved in regulating a plethora of cellular processes and functions. Dysregulation of isoprenoids and protein prenylation is implicated in various disorders, including cardiovascular and cerebrovascular diseases, cancers, bone diseases, infectious diseases, progeria, and neurodegenerative diseases including Alzheimer's disease (AD). Therefore, isoprenoids and/or prenyltransferases have emerged as attractive targets for developing therapeutic agents. Here, we provide a general overview of isoprenoid synthesis, the process of protein prenylation and the complexity of prenylated proteins, and pharmacological agents that regulate isoprenoids and protein prenylation. Recent findings that connect isoprenoids/protein prenylation with AD are summarized and potential applications of new prenylomic technologies for uncovering the role of prenylated proteins in the pathogenesis of AD are discussed.

Pharmacological interventions for the prevention of insufficiency fractures and avascular necrosis associated with pelvic radiotherapy in adults

BACKGROUND

Pelvic radiotherapy is a treatment delivered to an estimated 150,000 to 300,000 people annually across high-income countries. Fractures due to normal stresses on weakened bone due to radiotherapy are termed insufficiency fractures. Pelvic radiotherapy-related interruption of the blood supply to the hip is termed avascular necrosis and is another recognised complication. The reported incidences of insufficiency fractures are 2.7% to 89% and risk of developing avascular necrosis is 0.5%. These complications lead to significant morbidity in terms of pain, immobility and consequently risk of infections, pressure sores and mortality.

OBJECTIVES

To assess the effects of pharmacological interventions for preventing insufficiency fractures and avascular necrosis in adults over 18 years of age undergoing pelvic radiotherapy.

SEARCH METHODS

We performed electronic literature searches in the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase and DARE to 19 April 2017. We also searched trial registries. Further relevant studies were identified through handsearching of citation lists of included studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or non RCTs with concurrent comparison groups including quasi-RCTs, cluster RCTs, prospective cohort studies and case series of 30 or more participants were screened. We included studies assessing the effect of pharmacological interventions in adults over 18 years of age undergoing radical pelvic radiotherapy as part of anticancer treatment for a primary pelvic malignancy. We excluded studies involving radiotherapy for bone metastases. We assessed use of pharmacological interventions at any stage before or during pelvic radiotherapy. Interventions included calcium or vitamin D (or both) supplementation, bisphosphonates, selective oestrogen receptor modulators, hormone replacement therapy (oestrogen or testosterone), denosumab and calcitonin.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. We contacted study authors to obtain missing data. Data were to be pooled using the random-effects model if study comparisons were similar, otherwise results were to be reported narratively.

MAIN RESULTS

We included two RCTs (1167 participants). The first RCT compared zoledronic acid with placebo in 96 men undergoing pelvic radiotherapy for non-metastatic prostate cancer.The second RCT had four treatment arms, two of which evaluated zoledronic acid plus adjuvant androgen suppression compared with androgen suppression only in 1071 men undergoing pelvic radiotherapy for non-metastatic prostate cancer.Both studies were at a moderate to high risk of bias and all evidence was judged to be of very low certainty.The studies provided no evidence on the primary outcomes of the review and provided limited data in relation to secondary outcomes, such that meta-analyses were not possible. Both studies focused on interventions to improve bone health in relation to androgen deprivation rather than radiation-related insufficiency fractures and avascular necrosis. Few fractures were described in each study and those described were not specific to insufficiency fractures secondary to radiotherapy. Both studies reported that zoledronic acid in addition to androgen deprivation and pelvic radiotherapy led to improvements in BMD; however, the changes in BMD were measured and reported differently. There was no available evidence regarding adverse effects.

AUTHORS' CONCLUSIONS

The evidence relating to interventions to prevent insufficiency fractures and avascular necrosis associated with pelvic radiotherapy in adults is of very low certainty. This review highlights the need for prospective clinical trials using interventions prior to and during radiotherapy to prevent radiation-related bone morbidity, insufficiency fractures and avascular necrosis. Future trials could involve prospective assessment of bone health including BMD and bone turnover markers prior to pelvic radiotherapy. The interventions for investigation could begin as radiotherapy commences and remain ongoing for 12 to 24 months. Bone turnover markers and BMD could be used as surrogate markers for bone health in addition to radiographic imaging to report on presence of insufficiency fractures and development of avascular necrosis. Clinical assessments and patient reported outcomes would help to identify any associated adverse effects of treatment and quality of life outcomes.

Effect of zoledronate, a third-generation bisphosphonate, on proliferation and apoptosis of human dental pulp stem cells

Clinical use of zoledronate is accompanied by osteonecrosis of the jaw but the pathogenesis is not well understood. We assumed that zoledronate may have cytotoxicity against stem cells of the oral cavity and in this way helps to initiate or promote osteonecrosis. Dental pulp stem cells (DPSCs) and gingival fibroblasts (GFs) were isolated from volunteers who were undergoing a third molar extraction. The proliferation of DPSCs and GFs was evaluated using the thiazolyl blue tetrazolium bromide assay. The effect of zoledronate on apoptosis was determined by propidium iodide staining and Western blotting analysis. Incubation with zoledronate for 72 h and 7 days significantly decreased proliferation of DPSCs and GFs at concentrations of more than 0.4 μmol/L (p < 0.001). The IC50 of zoledronate was lower for DPSCs than for GFs (0.92 versus 3.5 μmol/L for 7 days of treatment). After 72 h of treatment with zoledronate, the percentage of apoptotic DPSCs significantly increased, which was accompanied by an increased level of pro-apoptotic proteins caspase-3 and Bax and decreased the level of the anti-apoptotic protein Bcl-2. In conclusion, zoledronate has anti-proliferative and pro-apoptotic effects in DPSCs. These effects may be involved in promoting zoledronate-induced osteonecrosis and suggest an unfavorable impact of this drug on regenerative potentials of the body stem cells.

Evaluation of the bisphosphonate effect on stem cells derived from jaw bone and long bone rabbit models: A pilot study

BACKGROUND AND OBJECTIVE

Bisphosphonates have been widely used and the number of patients experiencing medication-related osteonecrosis of the jaw (MRONJ) has been increasing. This study was designed to evaluate the effect of zoledronate on stem cells derived from different tissues.

DESIGN

Stem cells derived from four different tissues were compared using rabbit models (JPO: periosteum from the jaw bone (mandible), JBM: bone marrow from the jaw bone, LPO: periosteum from long bone (tibia), and LBM: bone marrow from long bone). Stem cells were grown in the presence of zoledronate at final concentrations ranging from 10-6M to 10-10M. Morphology was viewed under an inverted microscope, and the analysis of cell proliferation was performed using a Cell Counting Kit-8 (CCK-8) on days 1, 2, 4, and 7.

RESULTS

The CCK-8 results for LBM showed that the increase of CCK-8 values was correlated with a longer incubation time. Compared to the untreated control, growth in the presence of zoledronate at 10-10M and 10-8M resulted in decreased CCK-8 values for LBM on day 7 (P<0.05). The CCK-8 results for JBM, LPO, and JPO on days 1, 2, 4, and 7 showed that the presence of zoledronate did not produce statistically significant changes compared with the untreated control.

CONCLUSION

Zoledronate in the tested concentrations from JBM, LPO, and JPO did not produce noticeable alterations in the viability of mesenchymal stem cells. This in vitro experiment suggests that the occurrence of MRONJ solely in the oral cavity is not due to differences in the cellular proliferation of stem cells in the response to zoledronate.

Decoy TRAIL receptor CD264: a cell surface marker of cellular aging for human bone marrow-derived mesenchymal stem cells

BACKGROUND

Mesenchymal stem cells (MSCs) are a mixture of progenitors that are heterogeneous in their regenerative potential. Development of MSC therapies with consistent efficacy is hindered by the absence of an immunophenotype of MSC heterogeneity. This study evaluates decoy TRAIL receptor CD264 as potentially the first surface marker to detect cellular aging in heterogeneous MSC cultures.

METHODS

CD264 surface expression, regenerative potential, and metrics of cellular aging were assessed in vitro for marrow MSCs from 12 donors ages 20-60 years old. Male and female donors were age matched. Expression of CD264 was compared with that of p16, p21, and p53 during serial passage of MSCs.

RESULTS

When CD264⁺ cell content was 20% to 35%, MSC cultures from young (ages 20-40 years) and older (ages 45-60 years) donors proliferated rapidly and differentiated extensively. Older donor MSCs containing < 35% CD264⁺ cells had a small size and negligible senescence despite the donor's advanced chronological age. Above the 35% threshold, CD264 expression inversely correlated with proliferation and differentiation potential. When CD264⁺ cell content was 75%, MSCs were enlarged and mostly senescent with severely compromised regenerative potential. There was no correlation of the older donors' chronological age to either CD264⁺ cell content or the regenerative potential of the donor MSCs. CD264 was upregulated after p53 and had a similar expression profile to that of p21 during serial passage of MSCs. No sex-linked differences were detected in this study.

CONCLUSIONS

These results suggest that CD264 is a surface marker of cellular age for MSCs, not the chronological age of the MSC donor. CD264 is first upregulated in MSCs at an intermediate stage of cellular aging and remains upregulated as aging progresses towards senescence. The strong inverse correlation of CD264⁺ cell content to the regenerative potential of MSCs has possible application to assess the therapeutic potential of patient MSCs, standardize the composition and efficacy of MSC therapies, and facilitate aging research on MSCs.

Targeting subchondral bone mesenchymal stem cell activities for intrinsic joint repair in osteoarthritis

Osteoarthritis (OA) is a common age-related disease with complex pathophysiology. It is characterized by wide-ranging tissue damage and ultimate biomechanical failure of the whole joint. However, signs of tissue adaptation and attempted repair responses are evident in OA-affected osteochondral tissues. Highlighted in this review article is the role of bone-resident mesenchymal stem cells (MSCs) in these bone remodeling responses, and a proposal that targeting MSC activities in OA subchondral bone could represent a novel approach for intrinsic joint regeneration in OA. The development of these therapies will require better understanding of MSC proliferation, migration and differentiation patterns in relation to OA tissue damage and further clarification of the molecular signaling events in these MSCs during disease progression.

Osteoarthritis (OA) is a joint disorder, in which the cartilage, the underlying bone and other joint tissues are affected. Recent evidence demonstrating attempted repair responses in these OA tissues challenges the traditional view of OA as a degenerative disorder. Signs of tissue regeneration are particularly evident in the bone located directly underneath the damaged cartilage, where increased stem cell activity has been observed. Targeting these stem cells could represent a novel approach for intrinsic joint regeneration in OA. To progress with developing these novel therapies, a better understanding of stem cell function in normal and OA joint tissues is needed.

The Pharmacological Profile of a Novel Highly Potent Bisphosphonate, OX14 (1-Fluoro-2-(Imidazo-[1,2-α]Pyridin-3-yl)-Ethyl-Bisphosphonate)

Bisphosphonates are widely used in the treatment of clinical disorders characterized by increased bone resorption, including osteoporosis, Paget's disease, and the skeletal complications of malignancy. The antiresorptive potency of the nitrogen-containing bisphosphonates on bone in vivo is now recognized to depend upon two key properties, namely mineral binding affinity and inhibitory activity on farnesyl pyrophosphate synthase (FPPS), and these properties vary independently of each other in individual bisphosphonates. The better understanding of structure activity relationships among the bisphosphonates has enabled us to design a series of novel bisphosphonates with a range of mineral binding properties and antiresorptive potencies. Among these is a highly potent bisphosphonate, 1-fluoro-2-(imidazo-[1,2 alpha]pyridin-3-yl)-ethyl-bisphosphonate, also known as OX14, which is a strong inhibitor of FPPS, but has lower binding affinity for bone mineral than most of the commonly studied bisphosphonates. The aim of this work was to characterize OX14 pharmacologically in relation to several of the bisphosphonates currently used clinically. When OX14 was compared to zoledronate (ZOL), risedronate (RIS), and minodronate (MIN), it was as potent at inhibiting FPPS in vitro but had significantly lower binding affinity to hydroxyapatite (HAP) columns than ALN, ZOL, RIS, and MIN. When injected i.v. into growing Sprague Dawley rats, OX14 was excreted into the urine to a greater extent than the other bisphosphonates, indicating reduced short-term skeletal uptake and retention. In studies in both Sprague Dawley rats and C57BL/6J mice, OX14 inhibited bone resorption, with an antiresorptive potency equivalent to or greater than the comparator bisphosphonates. In the JJN3-NSG murine model of myeloma-induced bone disease, OX14 significantly prevented the formation of osteolytic lesions (p < 0.05). In summary, OX14 is a new, highly potent bisphosphonate with lower bone binding affinity than other clinically relevant bisphosphonates. This renders OX14 an interesting potential candidate for further development for its potential skeletal and nonskeletal benefits. © 2017 American Society for Bone and Mineral Research.

Rho inhibition by lovastatin affects apoptosis and DSB repair of primary human lung cells in vitro and lung tissue in vivo following fractionated irradiation

Thoracic radiotherapy causes damage of normal lung tissue, which limits the cumulative radiation dose and, hence, confines the anticancer efficacy of radiotherapy and impacts the quality of life of tumor patients. Ras-homologous (Rho) small GTPases regulate multiple stress responses and cell death. Therefore, we investigated whether pharmacological targeting of Rho signaling by the HMG-CoA-reductase inhibitor lovastatin influences ionizing radiation (IR)-induced toxicity in primary human lung fibroblasts, lung epithelial and lung microvascular endothelial cells in vitro and subchronic mouse lung tissue damage following hypo-fractionated irradiation (4x4 Gy). The statin improved the repair of radiation-induced DNA double-strand breaks (DSBs) in all cell types and, moreover, protected lung endothelial cells from IR-induced caspase-dependent apoptosis, likely involving p53-regulated mechanisms. Under the in vivo situation, treatment with lovastatin or the Rac1-specific small molecule inhibitor EHT1864 attenuated the IR-induced increase in breathing frequency and reduced the percentage of γH2AX and 53BP1-positive cells. This indicates that inhibition of Rac1 signaling lowers IR-induced residual DNA damage by promoting DNA repair. Moreover, lovastatin and EHT1864 protected lung tissue from IR-triggered apoptosis and mitigated the IR-stimulated increase in regenerative proliferation. Our data document beneficial anti-apoptotic and genoprotective effects of pharmacological targeting of Rho signaling following hypo-fractionated irradiation of lung cells in vitro and in vivo. Rac1-targeting drugs might be particular useful for supportive care in radiation oncology and, moreover, applicable to improve the anticancer efficacy of radiotherapy by widening the therapeutic window of thoracic radiation exposure.

Co-Activation of PKC-δ by CRIF1 Modulates Oxidative Stress in Bone Marrow Multipotent Mesenchymal Stromal Cells after Irradiation by Phosphorylating NRF2 Ser40

The high mortality associated with pancytopenia and multi-organ failure resulting from hematopoietic disorders of acute radiation syndrome (h-ARS) creates an urgent need for developing more effective treatment strategies. Here, we showed that bone marrow multipotent mesenchymal stromal cells (BMMSCs) effectively regulate oxidative stress following radiative injury, which might be on account of irradiation-induced elevation of protein levels of CR6-interacting factor 1(CRIF1) and nuclear factor E2-related factor 2(NRF2). Crif1-knockdown BMMSCs presented increased oxidative stress and apoptosis after irradiation, which were partially due to a suppressed antioxidant response mediated by decreased NRF2 nuclear translocation. Co-immunoprecipitation (Co-IP) experiments indicated that CRIF1 interacted with protein kinase C-δ (PKC-δ). NRF2 Ser40 phosphorylation was inhibited in Crif1-deficient BMMSCs even in the presence of three kinds of PKC agonists, suggesting that CRIF1 might co-activate PKC-δ to phosphorylate NRF2 Ser40. After radiative injury, the supporting effect of BMMSCs for the colony forming ability of HSCs in vitro was reduced, and the deficiency of CRIF1 aggravated such damage. Thus, CRIF1 plays an essential role in PKC-δ/NRF2 pathway modulation to alleviate oxidative stress in BMMSCs after irradiative injury, and at some level it may maintain the HSCs-supporting effect of BMMSCs after radiative injuries.

Mesenchymal Stem Cells as a Prospective Therapy for the Diabetic Foot

The diabetic foot is a serious complication of diabetes. Mesenchymal stem cells are an abundant source of stem cells which occupy a special position in cell therapies, and recent studies have suggested that mesenchymal stem cells can play essential roles in treatments for the diabetic foot. Here, we discuss the advances that have been made in mesenchymal stem cell treatments for this condition. The roles and functional mechanisms of mesenchymal stem cells in the diabetic foot are also summarized, and insights into current and future studies are presented.

Pretreatment with Bisphosphonate Enhances Osteogenesis of Bone Marrow Mesenchymal Stem Cells

Mesenchymal stem cell (MSC)-mediated bone regeneration is used to replace lost bone. However, methods to accelerate the process and stabilize regenerated bone remain limited. Therefore, we investigated the effect of bisphosphonates (BPs) on the function of bone marrow mesenchymal stem cells (BMMSCs) to determine if they might enhance MSC-mediated bone regeneration. We isolated and cultured BMMSCs from BALB/c mice and treated the cells with 0.1, 0.5, 1, 5, or 10 μM zoledronic acid (ZA; Zometa, a commercially available BP). ZA had a dose-dependent effect on BMMSCs proliferation and osteogenesis. ZA at concentrations of 5 and 10 μM inhibited the proliferation and osteogenic differentiation of BMMSCs. By contrast, in addition to inducing the proliferation and osteogenesis of BMMSCs, 0.5 μM ZA upregulated expressions of the osteogenesis-related genes Alp, osterix (Osx), and bone sialoprotein (Bsp) and enhanced osteogenesis in vivo when ZA-treated BMMSCs were implanted subcutaneously in nude mice. In addition, 0.5 μM ZA increased expression of Opg in BMMSCs, decreased the Rankl/Opg ratio, and decreased the number of osteoclasts. However, it was not associated with adverse effects on numbers of regulatory T cells or levels of Th17, transforming growth factor-β1 (TGF-β1), and interleukin-17a (IL-17a) when cocultured with T cells. In conclusion, 0.5 μM ZA pretreatment enhanced the proliferation and osteogenesis of BMMSCs in vitro and in vivo and decreased the number of osteoclasts without impairment of BMMSCs immunomodulatory properties. In vitro pretreatment of BMMSCs with BP and subsequent implantation may be a safe and effective way of enhancing MSC-mediated bone regeneration.

Small molecule-driven direct conversion of human pluripotent stem cells into functional osteoblasts

The abilities of human pluripotent stem cells (hPSCs) to proliferate without phenotypic alteration and to differentiate into tissue-specific progeny make them a promising cell source for regenerative medicine and development of physiologically relevant in vitro platforms. Despite this potential, efficient conversion of hPSCs into tissue-specific cells still remains a challenge. Herein, we report direct conversion of hPSCs into functional osteoblasts through the use of adenosine, a naturally occurring nucleoside in the human body. The hPSCs treated with adenosine not only expressed the molecular signatures of osteoblasts but also produced calcified bone matrix. Our findings show that the adenosine-mediated osteogenesis of hPSCs involved the adenosine A2bR. When implanted in vivo, using macroporous synthetic matrices, the human induced pluripotent stem cell (hiPSC)-derived donor cells participated in the repair of critical-sized bone defects through the formation of neobone tissue without teratoma formation. The newly formed bone tissues exhibited various attributes of the native tissue, including vascularization and bone resorption. To our knowledge, this is the first demonstration of adenosine-induced differentiation of hPSCs into functional osteoblasts and their subsequent use to regenerate bone tissues in vivo. This approach that uses a physiologically relevant single small molecule to generate hPSC-derived progenitor cells is highly appealing because of its simplicity, cost-effectiveness, scalability, and impact in cell manufacturing, all of which are decisive factors for successful translational applications of hPSCs.